Lactate- or bicarbonate-buffered solutions in continuous extracorporeal renal replacement therapies

Background. Continuous renal replacement therapies (CRRTs) are well accepte d for critically ill patients with acute renal failure (ARF). Today, daily fluid exchange in CRRT reaches 30 to 40 liter and more. Therefore, the comp osition of the substitution/dialysate fluid, often primarily developed eith er for intermittent treatment or for peritoneal dialysis, becomes more rele vant. Lactate (30 to 45 mmol/liter) is frequently used as the buffer becaus e of the high stability of this substance. However, lactate is thought to h ave negative effects on metabolic and hemodynamic parameters. Methods. Published data for different substitution fluids are presented wit h respect to acidosis and lactate concentration, uremia, and hemodynamic an d metabolic alterations. Results. Only a few studies compare substitution fluids with different buff ers. Uremia and acidosis (pH, base excess) were sufficiently controlled dur ing CRRT with an exchange volume of in average 30 liters using either buffe r. Lf patients with severe liver failure and lactic acidosis were excluded, no difference in hemodynamic and metabolic parameters between the solution s occurred. The plasma lactate concentration was elevated during lactate us e in some cases, but lactate levels remained within normal limits in patien ts without liver impairment. The bicarbonate concentration in the solutions should exceed 35 to 40 mmol/liter, as in some cases the buffer capacity of the solutions was inadequate. In patients with severe liver failure or lac tic acidosis, solutions with lactate buffer were shown not to be indicated. Conclusion. In patients with reduced lactate metabolism, for example, conco mitant severe liver failure, after Liver transplantation or in lactic acido sis, bicarbonate-buffered solutions should be used. In nearly all other cas es of critically ill patients with ARF, lactate-buffered solutions may be u sed as well as bicarbonate solutions.